Disturbance switch



April 28, 1970 R. F. KIRK mswunsmcm SWITCH Filed July 24, 1968 [I3 UTI LIZ-ATION CIRCUIT W m m w INVENTOR.

I RUSSELL E KIRK (mm i zfiwek BY ATTORNEY US. Cl. ZOO-61.45

3,509,298 Patented Apr. 28, 1970 3,509,298 DISTURBAN CE SWITCH I Russell F. Kirk, Sunnyvale, Calif., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed July 24, 1968, Ser. No. 747,301 Int. Cl. H01h 35/14 Claims ABSTRACT OF THE DISCLOSURE A normally open electrical switch which closes momentarily when subjected to disturbance forces. The switch has a center post as one terminal and a coaxial housing to which the other terminal is connected. An annular cavity within the housing about the post contains an electrical contact ball and is shaped to cause the ball to rest by gravity against the housing spaced from the center post for any physical position of the assembly. A disturbance force against the switch causes the ball to momentarily shift against both the post and the housing to close the contacts.

BACKGROUND OF THE INVENTION The invention herein described was made in the course of or under a contract or subcontract thereunder (or grant), with the Department of the Army.

This invention relates to electrical switches, and more particularly to a disturbance switch which closes momentarily when subjected to a disturbance force.

A disturbance switch is an electro-mechanical device which responds to acceleration forces applied to it or an attached parent body by momentarily closing normally open electrical contacts. These switches operate in any physical position. The contacts are held open by gravity SUMMARY OF INVENTION The center post or hub of the switch assembly constitutes both a structural element for mechanically mounting switch parts, an electrical contact for the switch, and a terminal. The post is formed to properly space other switch components and at the same time to define one wall of a cavity in which a spherical contact ball or balls are disposed. The clearance between this post and the balls when the latter are at rest in the cavity is sufficient to maintain the switch in an open position. Sudden movement of the switch causes the balls to make a momentary electrical contact between the center post and the other terminal and afterward return to the normally open position.

DESCRIPTION OF THE DRAWINGS FIGURE 1 has a side elevation of a disturbance switch embodying this invention;

FIGURE 2 is a transverse section taken on line 2-2 of FIGURE 1;

FIGURE 3 is a section of part of the casing wall showing a modified form of the invention;

FIGURE 4 is a transverse section taken on line 44 of FIGURE 1; and

FIGURE 5 is a. section taken on line 5-5 of FIG- URE 2.

DESCRIPTION OF PREFERRED EMBODIMENTS A preferred embodiment of the invention is shown in FIGURE 1 as a disturbance switch 10 having terminals 11a and 12 connected to a utilization circuit 13 which is adapted to respond to the closing of the switch when the latter is disturbed. Terminals 11 and 12 project from one end of a cylindrically shaped housing 14 having a central axis A coincident with the axis of terminal 11.

Housing 14 comprises a cup shaped casing 16, see FIG- URE 5, and headers 17 and 18 within the casing and axially spaced from each other to define an annular cavity 20 with a generally trapezoidally-shaped cross section. The casing and headers are electrically conductive members. The opposed surfaces 21 and 22 of headers 17 and 18, respectively, diverge from each other at an angle at radially outwardly from axis A.

Terminal 11a is the exterior extension of a center post 11 which has an enlarged central portion 25 defined by shoulders 26 and 27 and a cylindrical surface 28. The parts of post 11 having reduced diameters and extending axially from central portion 25 are supported in substantially identical bushing-like insulators 29 and 30 mounted in bores 31 and 32 of headers 17 and 18, respectively, and insulating post 11 from the headers. Insulators 29 and 30 have external shoulders 29a and 30a which engage corresponding shoulders in bores 31 and 32, respectively, for properly spacing the parts of the switch assembly within casing 16. The axial length of insulator 29 is greater than the reduced portion of the post it engages so as to space the inner end of the post from casing 16. Header 18 has an external shoulder 33 which engages the end edge of casing 16 to further insure that the relative ositioning of the switch assembly parts is accurate. Terminal 12 is electrically connected to header 18, preferably by a press fit in header recess 35.

Cavity 20 contains one or preferably two conductive spheres or balls 37 which are adapted to move freely circumferentially and radially within the cavity. More precisely, the diameter of each ball 37 is less than the radial depth and axial height of the cavity so that the ball does not engage the central post portion 25 and casing 16 at the same time; The diameter of each ball is sufliciently large, however, to make simultaneous electrical contact with one of the headers 17 or 18 and the central post portion 25 when the ball is positioned on one of the inner corners of the cavity.

The inclination of header surfaces 21 and 22 together with the annular shape of the cavity causes each ball 37 to rest against casing 16 out of contact with post portion 25 as indicated in solid lines in FIGURES 2 and 5. However, rapid acceleration or deceleration of the switch assembly as a result of a disturbance force applied to it from any direction causes the balls to move inwardly to either or both of the broken line positions indicated in FIGURE 5 and momentarily make an electrical connection between post portion 25 and one of the headers 17 or 1-8. This corresponds to a momentary closing of the switch and short-circuiting of terminals 11a and 12 so as to produce the desired effect in utilization circuit 13. When the switch assembly is at rest, the balls return to their original solid line positions and the switch is again in its normally open state.

In order to prevent the balls 37 from remaining out of contact with the post 25 while rolling about the interior of cavity 20, a plurality of inwardly extending projections or bumpers 39' are mounted on the inner surface of the casing within the cavity at arcuately spaced intervals. These bumpers are radially spaced from post portion 25 by a distance greater than the diameter of each ball and serve to divert the moving ball inwardly to an'operative contact-closing position. Bumpers 33 may be separate inserts locatedfwithinthe cavity or may be inwardly extending ridges 40, see FIGURE 3, formed in "the' central portion of the casing after assembly of the sures their proper relative spacing without precision assembly tools. The functional parts of the switch including casing 16 also substantially completely seal the interior cavity 20 and balls 37 against moisture and dust and thus insure a long shelf or field life for the switch.

What is claimed is:

1. A disturbance switch comprising, in combination:

a conductive casing having an axis,

first and second axially spaced conductive headers mounted in and electrically connected to said casing, said headers having axially aligned bores and opposed axially spaced outwardly diverging surfaces defining with said casing an annular radially outwardly expanding cavity,

a coaxial conductive center post mounted in the bores of said headers and insulated therefrom and from said casing, said post having a central portion between and spaced from said headers defining an inner wall of said cavity, and

a conductive sphere disposed for free movement in said cavity, said sphere normally being positioned against said casing spaced from said post when the switch is at rest and momentarily simultaneously engaging one of said headers and the central portion of said post when the switch is subjected to a disturbance force whereby to electrically connect said post and said one header.

2. The switch according to claim 1 in which said casing is cylindrically shaped and closed at one end.

3. The switch according to claim 2 with substantially "identicalbushing-like insulators mounted'in'the bores of has a minimum number of relatively inexpensive parts. "Center post 25 is essentially a structural column about which the other switch parts are symmetrically supported, thereby providing a rugged compact unit. All of the parts are relatively inexpensive to manufacture and the provision of intregal self-locating shoulders on the parts intral portion of'said post has a diameter greaterrthan adjacent portions thereof, said. central post portion being defined by axially'spa'ced shoulders engagable with the inner ends of said insulators whereby to axially space said insulators and in turnsaid headers.

5. A disturbance switch comprising:

a cylindrical conductive cup i a conductive post insulated from and extending coaxially within and without said cup,

a pair of washer-like conductive headers insulated from said post and axially spaced with in and en gaging said cup,

the axial spacing between said headers increasing at radially greater distances from the post whereby to define an annular radially outwardly diverging cavity, I v I a conductive ball within said cavity and having a diameter less than the transverse dimension of said cavity and sufficiently large to make simultaneous electrical contact with said post and one of said headers, and

means for externally electrically connecting said post and one of said headers,

US. Cl. X.R. 10270.2 

